Bacteriorhodopsin (BR) is a retinal protein molecule found in the photosynthetic system of a salt-marsh bacterium called Halobacterium salinarium. The BR molecules are located in the cell membrane, forming a 2D protein-lipid array, commonly called the purple membrane. The use of photochromic proteins like bacteriorhodopsin (BR) for optical data storage has been considered promising.
Proteorhodopsins (PRs) are distantly related to bacteriorhodopsin (BR) (22-24% sequence identity). Proteorhodopsins are integral membrane proteins; they are isolated from uncultivated marine eubacteria and function as light-driven proton pumps. Upon absorption of light by the all-trans-retinal co-factor, proteorhodopsin goes through a photocycle with a number of intermediates. It is believed that upon excitation of the proteorhodopsin molecule by light stimulation, a proteorhodopsin/retinal complex is excited to an unstable intermediate energy state. Proteorhodopsin progresses through a series of unstable energy states that can vary in terms of energy plateaus or intermediates, e.g., an “M-like state” or “M-state”, a “K-like state” or “K-state”, an (“N-like state” or “N-state”, or an “O-like state” or “O-state”. Subsequently, the complex reverts to a more stable basal state concomitant with transport of a proton.
Béjà, et al. (Science 289:1902-6, 2000) disclose the cloning of a proteorhodopsin gene from an uncultivated member of the marine γ-proteobacteria (i.e., the “SAR86” group). The proteorhodopsin was functionally expressed in E. coli and bound all-trans-retinal to form an active light-driven proton pump.
Béjà, et al. (Nature 411:786-9, 2001) disclose the cloning of over twenty variant proteorhodopsin genes from various sources. The proteorhodopsin variants appear to belong to an extensive family of globally distributed proteorhodopsin variants that maximally absorb light at different wavelengths.
Dioumaev, et al. (Biochemistry, 42: 6582-6587 (2003)) disclose using proteorhodopsin-containing membrane fragments encased in polyacrylamide gel for flash photolysis and measurements of absorption changes in the visible range.
U.S. Pat. No. 5,235,076 (Asato) discloses azulenic retinoid compounds and therapeutic compositions. The compositions are useful in treating dermatological disorders such as acne and psoriasis.
U.S. Pat. No. 4,896,049 (Ogawa) discloses various synthetic analogs of retinal, which have different absorption wavelengths. The synthetic retinal analogs disclosed in Ogawa are incorporated herein by reference.
Khodonov, et al. (Sensors and Actuators B 38-39:218-221 (1997)) describe modified bacteriorhodopsin by replacing the natural bacteriorhodopsin chromophore, all-trans-retinal, with its analogs. The retinal analogs disclosed in Khodonov are incorporated herein by reference.
Imai, et al. (Photochemistry and Photobiology, 70: 111-115 (1999)) disclose that azulenic retinal analogs failed to yield a red-shifted visual pigment analog, whereas the 9-cis isomers of the polyenals 3-methoxy-3-dehydroretinal and 14F-3-methoxy-3-dehydroretinal yielded iodopsin pigment analogs at 663 and 720 nm.
U.S. Pat. No. 6,483,735 (Rentzepis) discloses a three- or four-dimensional radiation memory that serves to store multiple binary bits of information in the same physical volumes of each of a multiplicity of addressable domains in each of potentially multiple layers within the entire volume of a planar disc, or in a random-access volume radiation memory. The storage of multiple information bits within the same addressable domains is done by the co-location of several different florescent chemical compounds in the volume of each such domain; the florescent chemical compounds are not rewriteable.
U.S. Pat. Nos. 5,470,690 and 5,346,789 (Lewis) disclose a stable, image-retaining, optically switchable film containing bacteriorhodopsin obtained from Halobacterium Halobium (currently known as Halobacterium salinarum) in a high-pH polyvinyl alcohol solution for an optical memory for data storage.
Gourevich, I. et al. (Chemical Materials, Multidye Nanostructured Material for Optical Data Storage and Security Labeling (2004)) disclose a polymer nanocomposite for three-dimensional optical data storage and security labeling using visible and near-IR fluorescent dyes. The data is written via selective photobleaching of the fluorescent dyes, which are not rewriteable.
Optical data storage has the potential to revolutionize the computer industry, since optical data storage provides both a very high storage capacity and rapid reading and writing of data. Additionally, optical signal processing could be used in a highly parallel fashion for pattern recognition, which is difficult to do with the current computing technologies. A functional optical material with low light scattering, large data storage capacity, and rewriteable capacity is required for these applications to succeed.
Documents like banknotes, checks, identity cards, etc. often incorporate security features to make them difficult to copy or counterfeit. Most of these are based on either using special paper with security features like watermarks incorporated during paper manufacturing, or printing hairline patterns that are difficult to copy. However, such features are permanently visible and do not meet sophisticated security requirements.
There are needs for optical information carriers that can be produced efficiently and economically and have low background noise (crosstalk), large data storage capacity, and rewriteable capacity. Such optical information carriers are effective as optical data storage material or fraud-proof optical data carriers.